Semiconductor device having a tapeless mounting

ABSTRACT

A semiconductor device having a photosensitive thermosetting resin layer 64 provided on top of a protective film 13 for a semiconductor chip 10. A lead frame 11 is affixed to the surface of this photosensitive thermosetting resin layer 64 only at support pin sections 60, 61, and this lead frame 11 is electrically connected to the surface of semiconductor chip 10. Breakage of the wiring and chip cracking are prevented after the pressure-bonding mounting of the lead frame. Because package cracking and package warping are better controlled in thermal processes such as such as IR reflow and resin sealing, a lower cost semiconductor device and manufacturing method are enabled.

FIELD OF THE INVENTION

This invention relates to semiconductor devices in Lead On Chip (LOC)packages and a methods of making them.

BACKGROUND OF THE INVENTION

One conventional way to seal an IC chip in a package is to provide anLOC construction wherein a lead frame is affixed on the circuit-formingsurface of the IC chip, for example as shown in FIGS. 28 and 29.

In FIGS. 28 and 29, a package for a LOC construction of, for example, aDRAM (dynamic RAM) is shown, with a large number of bonding pads 1 beingarranged on a straight line in the center of the semiconductorintegrated circuit (IC) chip 10. The power supply lines 42, 43, whichare called bus bars, and a large number of signal lines 44, 45, arerespectively arranged on both sides of this pad line, forming the leadframe 11 used for the LOC. This lead frame is formed from an iron-nickelalloy, a copper alloy, copper, or the like.

The bus bars 42, 43 are connected to the power supply Vss or Vcc, andthe signal lines 44, 45 are used for the various signals such as theaddresses A0 to A10, CAS, and RAS.

The connections between each bonding pad 1 and each wire is accomplishedby means of the respective wire bonding by means of bonding wires 6, 7on one side of the bonding pad line, and by bonding wires 8, 9 on theother side. In this case, the wires 7, 9 that connect the signal lines44, 45 (specifically, the inner lead section) straddles on top of thebus bars 42, 43. Also, the entire body is sealed by means of a moldingresin 18 (in FIG. 28, shown by the virtual line) consisting of an epoxyresin or the like, with the outer lead section 45a being led to theoutside of this molding resin.

In the package for the IC chip 10 made in this manner, the lead frame 11is affixed on top of the IC chip 10 (specifically, on top of the circuitforming surface) by means of the LOC construction; details are explainedwith FIG. 29.

First, with regard to the IC chip 10, for example, a passivation film(protective film) 13 comprising a laminated film of SiO₂ and Si₃ N₄, forexample, SiO₂ and Si₃ N₄ is provided on one main face of the siliconsubstrate 12, bonding pads 1 are formed in the window sections of thispassivation film and connected to the internal circuits of the IC chip10, then a thermosetting polyimide protective film 14 is adhered on theentire surface, except for this bonding pad region.

A filler is contained in the molding resin 18 (for example, additionalSiO₂ for the purpose of reducing the thermal expansion coefficient), butbecause a filler made in this manner contains radioactive elements suchas uranium and thorium, which radiate α-rays, the so-called soft errorsare easily generated wherein the α-rays from these radioactive elementsare irradiated on the IC chip 10 and the circuit operates erroneously.The polyimide protective film 14 in particular prevents the invasion ofthe α-rays generated in that manner, and is provided to prevent defectsdue to soft errors.

The process that forms the polyimide protective film 14 on top of thepassivation film 13, which consists of the laminated film of Si₃ N₄ film13A and SiO₂ film 13B, is shown summarized in FIGS. 30-33.

First, after the passivation film 13 is selectively etched (FIG. 30) toexpose the bonding pads 1, a noncured thermosetting polyimide resin 14Ais coated on the entire surface (FIG. 31.

Next, an etching mask 20 is formed in the prescribed pattern byultraviolet radiation and a developing process (FIG. 32). Using thismask 20, the polyimide resin 14A is wet etched, the bonding pads 1 areexposed (FIG. 33) and, after the removal of the mask 20, curing isperformed, producing the polyimide protective film 14.

As shown in FIG. 29, frame 11 is adhered on top of the polyimideprotective film 14 by means of the double-faced adhesive type ofinsulating tape 15 (but, in FIG. 28, the insulating tape 15 is omittedfrom the illustration). This insulating tape 15 is a tape whereinadhesives (for example, thermoplastic adhesives) 17, 19 are respectivelypainted on both faces of the insulating film substrate 16, lead frame 11is adhered to the substrate 16 under heat and pressure by means of oneof the adhesives 17, and the substrate 16 is adhered on top of thepolyimide protective film 14 for the IC chip 10 under heat and pressureby means of the other adhesive 19. In this manner, the lead frame 11 ismounted and pressure bonded on top of the IC chip 10 by means of theinsulating tape 15.

However, because the lead frame 11 is affixed on top of the IC chip 10by means of the insulating tape 15, in addition to the thickness of theinsulating film substrate 16 being, for example, 50 μm, the thickness ofthe adhesives 17, 19 on both of its faces is, for example 12.5 μm,respectively. Therefore, because the combined thickness of theinsulating tape 15 becomes as much as 75 μm (depending on thecircumstances, 75 to 175 μm), the fact is clear that the various defects(a) to (d) presented below are mainly generated.

(a) Breaks are generated in the metal wiring during the mountingpressure and temperature cycles.

During pressure mounting for the lead frame 11, the stress that is shownby the following formula is generated: ##EQU1## where Tm: temperature(°C.) during mounting

-65°: minimum temperature (°C.) during the thermal cycle

E: modulus of elasticity of the insulating tape including the adhesives

α₂ : thermal expansion coefficient of the insulating tape including theadhesives

α₁ : thermal expansion coefficient of the silicon substrate of the ICchip

h: thickness (μm) of the insulating tape including the adhesives

W: width (μm) of the insulating tape including the adhesives

According to this equation for stress, if the thickness and the thermalexpansion coefficient of the insulating tape 15 including the adhesivesare large, the stress during the mounting pressure of the lead frameeasily becomes large. In the case of the mounting pressure of the leadframe 11, because the insulating tape 15 is used, due to the thicknessand thermal expansion coefficient of this insulating tape 15, as isshown in FIG. 34, cracks 23 are generated in the IC chip 10,particularly from the outer edge to the inner portion of the insulatingtape 15, and there are instances in which the metal wiring 24 breaks.

(b) The generation of package cracks originating in the expansion of theinsulating tape, which are generated during IR reflow.

At the time of affixing the completed IC package on top of the printedcircuit wiring board 26, for example, as shown in FIG. 37, as a methodof bonding the outer lead section 45a or 44a to the circuit pattern 27by means of solder, there is the IR reflow method that conducts bondingby means of infrared ray (IR) heating. At the time of IR reflow, the ICpackage is heated to about 245° C. at its peak.

Currently, the glass transition point (Tg) of the insulating tape isdesigned to be 210° C. In order to prevent the oxidation of the leadframe 11, it is preferable that the temperature at which the lead frame11 is glued to the chip 10 be made less than 400° C., but it isnecessary that this gluing temperature be above the glass transitiontemperature of the thermosetting adhesives 17, 19 of the insulating tape15 +150° C. It is for this reason that the glass transition point of theinsulating tape 15 is designed to be 210° C.

However, as for this glass transition point (210° C.), since it is lowerthan the IR reflow temperature (245° C.), as shown in FIG. 35, theadhesive makes the transition to a near liquid rubber condition duringIR reflow, and its adhesive function is remarkably decreased. Due tothis, during IR reflow, package cracks are easily generated.

On the other hand, because the combined thickness (75 μm) of theinsulating tape 15 is large, the percentage of moisture absorption ofthe tape itself (below 85° C., 85% humidity) becomes as high as 2 to2.5%. If the package is left to set for a long time in the air, the tapeabsorbs moisture, and as shown in FIG. 36, swelling is easily generatedin the adhesives 17 and 19. This causes crack 25 to be generated insealing resin 18 during IR reflow, and generates package cracks evenmore easily. It was confirmed that package cracks appeared in 16 out of120 samples.

(c) Generation of package warpage.

As for the size of each section shown by A', B', C', D', B', F', H', I',and J' in FIG. 29, specifically, these are as shown in the followingTable I. Here, these are shown for both a TSOP (Thin Small OutlinePackage) with a total thickness of about 1 mm (1000 μm) and an SOJ(Single Outline J-Lead Package) with a total thickness of about 2.7 mm(2700 μm).

                  TABLE I                                                         ______________________________________                                        1 mm TSOP           2.7 mm SOJ                                                ______________________________________                                        A'     0.195 mm (195 μm)                                                                           0.810 mm (810 μm)                                  B'     0.125 mm (125 μm)                                                                           0.200 mm (200 μm)                                  C'     0.075 mm (75 μm)                                                                            0.075 mm (75 μm)                                   D'     0.010 mm (10 μm)                                                                            0.010 mm (10 μm)                                   E'     0.280 mm (280 μm)                                                                           0.280 mm (280 μm)                                  F'     0.325 mm (325 μm)                                                                           1.335 mm (1335 μm)                                 H'     0.395 mm (395 μm)                                                                           1.085 mm (1085 μm)                                 I'     0.325 mm (325 μm)                                                                           1.335 mm (1335 μm)                                 J'     15.240 mm (15,240 μm)                                                                       15.240 mm (15,240 μm)                              ______________________________________                                    

Because the thickness (C'=75 μm) of insulating tape 15 is large, it isdifficult to adopt a construction balance in the package. In particular,in the case of a TSOP package or the like with a 1 mm thickness, thebowing referred to as package warpage originating in the tape thickness(greater than 75 μm) is easily generated.

In the 1-mm TSOP package used until now, it is difficult to make theresin thickness (A') on top of the lead frame less than 195 μm, but thisis because of the capabilities of the wire bonder and to prevent theprotrusion of the wire loop outside the package. Because of this, whenthe IC chip thickness (B') is made 280 μm, the resin thickness on top ofthe chip becomes H'=395 μm and the resin thickness beneath the chipbecomes I'=325 μm. This unbalanced thickness relationship is naturallygenerated due to the insulating tape thickness being C'=75 μm, andbrings about the problem of package warpage.

Due to the generation of this type of package warpage, shown inexaggerated form in FIG. 37, the package is warped 30-60 μm, the outerlead sections 45a or 44a on both edges in particular rise up in relationto the circuit pattern 27 on top of the printed wiring board 26, andthere are instances when these do not connect.

(d) Cost increases.

Insulating tape 15 that adheres the lead frame 11 has a high value ofabove several tens of yen per single unit, the cost of packages usingthis rises, and there are limitations to its cost reduction.

Thus, the present applicants, to eliminate the types of defects, inJapanese Patent Application No. Hei 6[1994]-27367, proposed asemiconductor device and its manufacturing method (hereinafter, referredto as the invention of the previous application) for a packageconstruction that can prevent the chip cracking and breakage of thewiring during the pressure bonded mounting and thermal cycles for thelead frame, that can control the package cracking and package warpage inprocesses such as IR reflow, and that can be manufactured at a low cost.

In other words, the invention of the previous application relates to asemiconductor device wherein a second protective film (in particular, asecond protective film that alleviates the influence of the α-rays dueto the filler of the molding resin) is provided on top of the protectivefilm for the semiconductor chip, the lead frame is affixed on top ofthis second protective film, and this lead frame is electricallyconnected to the surface of the semiconductor chip, with the maincomponents of the lead frame being affixed on top of the secondprotective film with a thermoplastic resin layer interposed and formingat least one portion of the second protective film.

In the semiconductor device of the invention of the previousapplication, the second protective film can be formed by means of alaminated body of a thermosetting polyimide resin layer, which becomesthe bottom layer, and a thermoplastic polyimide resin layer, whichbecomes the upper layer.

In this case, in the laminated body, in the region wherein the leadframe is adhered, the thermoplastic polyimide resin layer and thethermosetting polyimide resin layer are formed in almost the samepattern. The thickness of the thermoplastic polyimide resin layer is15-35 μm, the thickness of the thermosetting polyimide resin layer is 10to 30 μm, and in the region where the lead frame is not adhered, thethickness of the thermosetting polyimide resin layer can be 5-15 μm.

Also, in the laminated body, the thermoplastic polyimide resin layer canalso be provided on top of the thermosetting polyimide resin layer inthe regions where the lead frame is not adhered. The thickness of thethermoplastic polyimide resin layer can be 15-35 μm, and the thicknessof the thermosetting polyimide resin layer can be 10-30 μm.

In either case, the total thickness of the laminated body within thelead frame adhesion regions can be 35 to 65 μm.

In the semiconductor device of the invention of the previousapplication, the second protective layer can be made of only thethermoplastic polyimide resin layer.

In this case, the thickness of the thermoplastic polyimide resin layercan be 30-50 μm. Also, it is preferable that the thermoplastic polyimideresin layer also be provided on top of regions where the lead frame isnot adhered.

In the semiconductor device of the invention of the previousapplication, it is also permissible if the edges of the thermoplasticpolyimide resin layer within the lead frame adhesion regions protrude0.1 to 0.15 mm more than the edge of the lead frame (specifically, thewidth of the thermoplastic polyimide resin layer is made 0.1 to 0.15 mmlarger on each side in relation to the width of the lead frame).

Also, the spacing between the cell section of the semiconductor chip andthe edge of the thermoplastic resin layer can be 100 to 500 μm on theside of the bonding pad for the semiconductor chip.

Also, the thermoplastic resin layer and/or the thermosetting resin layercan be present in the regions of the bonding pad.

As for the semiconductor device of the invention of the previousapplication, in actuality, the bonding pad and the lead frame are wirebonded, and the entire body can be sealed with a molding resin. Also,the lead frame can comprise the lead frame section used for the signallines and the lead frame section used for the power-supply lines.

In the manufacture of the semiconductor device of the invention of theprevious application, at least a thermoplastic resin is coated on top ofthe protective film for the semiconductor chip. This coated resin ispatterned, and it is preferable that the lead frame be adhered on top ofthe thermoplastic resin layer after the curing is accomplished.

In this case, in practice, after the lead frame is adhered, the bondingpads of the semiconductor chip with the lead frame are wire bonded, thenthe entire body can be sealed with a molding resin.

Next, a concrete example of the invention of the previous application isexplained based on FIGS. 38-46. This example is a device wherein theinvention of the previous application was applied, for example, to apackage for a DRAM, the same keys are applied to the components that arethe same as in the prior example shown in FIGS. 28-37, so theirexplanations are omitted.

First, to explain the construction of the package of an LOC constructionbased on this example in FIGS. 38 and 39, the distinctive feature ofthis package is the fact that the thermoplastic polyimide resin layer 54is laminated on top of the passivation film 13 of the IC chip 10. Usingthat thermoplasticity, the bus bars 42, 43 and the signal lines 44, 45(inner lead section) of the lead frame 11 on top of this are bonded bythermal pressure (pressure-bonding mounted).

In other words, the thermoplastic polyimide resin layer 54 provided ontop of the IC chip, along with functioning as a second protective filmin the same manner as the previously mentioned polyimide protective film14, is used as an adhesive for the lead frame 11, and the point at whichthe insulating tape 15 like that previously mentioned is not used is afact that should be noted.

According to this example, as shown in FIGS. 38 and 39, the secondprotective layer is formed by means of only the thermoplastic polyimideresin layer 54. This resin layer 54 is provided across almost the entireregion of the memory cell section of the IC, as shown by the diagonallines in FIG. 39.

Also, it is preferable for the thickness (b) of the polyimide resinlayer 54 to be 20-45 μm. The glass transition point of the thermoplasticpolyimide resin layer 54 should be 210° C. The reason for this is that,in the same manner as presented above, the temperature at the time ofthermal pressure bonding of the lead frame on the IC chip surface isless than 400° C., with the wire bonding temperature being 200° C.

Also, when looked at in regard to the entire body of the package,specifically, the size of each component can be designed as shown in thefollowing Table II.

                  TABLE II                                                        ______________________________________                                        1 mm TSOP           2.7 mm SOJ                                                ______________________________________                                        A      0.195 mm (195 μm)                                                                           0.810 mm (810 μm)                                  B      0.125 mm (125 μm)                                                                           0.200 mm (200 μm)                                  b      0.030 mm (30 μm)                                                                            0.030 mm (30 μm)                                   E      0.280 mm (280 μm)                                                                           0.280 mm (280 μm)                                  F      0.370 mm (370 μm)                                                                           1.380 mm (1380 μm)                                 H      0.350 mm (350 μm)                                                                           1.040 mm (1040 μm)                                 I      0.370 mm (370 μm)                                                                           1.380 mm (1380 μm)                                 J      15.240 mm (15,240 μm)                                                                       15.240 mm (15,240 μm)                              ______________________________________                                    

As for the package based on this example, because it is a constructionwherein the lead frame 11 is directly pressure-bonding-mounted on top ofthe thermoplastic polyimide resin layer 54 used as the protective film,the following effects (A)-(E) can be obtained.

(A) The metal wiring breaks that are generated after the pressure-bondedmounting and during the thermal cycles can be prevented.

Because the insulating tape used in the conventional mounting was athickness of 75 to 175 μm, the thermal stress was large, but because thethickness of the polyimide resin layer 54 is as little as 30-50 μm, thetension stress can be lowered as much as 30% compared to theconventional type.

Specifically, in the package internal section, the maximum stress isconcentrated in the chip surface region directly beneath the cornersection (P) of the bus bar shown in FIG. 39. Due to this, the tensilestress exerts a harmful influence on the device characteristics. Whenthe tensile stress on top of the chip surface was found during a thermalcycle of 150° C. to -65° C., in the structure of FIG. 38, a tensilestress of 2.90 kg/mm² was shown. It can be seen that it decreased about30%, compared to a tensile stress of 4.20 kg/mm² in the construction ofFIG. 29 based on the conventional example.

(B) The package cracks that tend to be generated during IR reflow can beprevented.

Accompanying the capability to reduce the volume of the adhesive layer(polyimide resin layer), since the percentage of water absorption isreduced, the generation of package cracks during IR reflow can beremarkably reduced or prevented. In this case, there were absolutely nopackage cracks for a sampling of 120 units.

(C) Package warpage can be prevented.

Specifically, in a 1-mm TSOP or the like, a balance of the resinthickness above and below the chip within the package is easily obtaineddue to the equilibrium between the thicknesses (H) and (I), and thepackage warpage can be made less than 20 μm or sufficiently prevented.

(D) A cost reduction can be realized.

Compared to the cost of the insulating tape (attached to the lead frame)used until now, in the mounting construction based on this example, the[cost] per unit can be reduced to less than about 1/7 to 1/33.

(E) Soft errors can be effectively prevented.

By providing the thermoplastic polyimide resin layer 54 at a thicknessof above 30 μm across the entire region of the cell section, the cellsection is physically shielded from the previously mentioned α-rays.Therefore, the α-rays radiated from the lead frame and the filler (SiO₂and the like) within the molding resin 18 are effectively shielded, andsoft errors of the memory cell section can be prevented.

The thermoplastic polyimide resin 54 used here has the followingphysical values, and can be of the construction shown in FIG. 40.

Tensile strength 10 kg/mm² (room temperature)

Tensile modulus of elasticity 280 kg/mm² (room temperature)

Tensile coefficient of elongation 10% (room temperature)

Volume resistivity 6.3×10¹⁶ Ω-cm

Leakage current value 1.61×10⁻¹¹ (A) (room temperature) 1.07×10⁻¹¹ (A)(PCT after 500 h)

(The PCT (Pressure Coupler Test) test is one stress testing methodwherein the body to be tested is placed at a pressure of 1 atm and at121° C., and the changes in various characteristics before and afterthat are observed.)

Pyrolysis temperature 520° C.

Thermal expansion coefficient 4.3×10⁻⁵ (1/°C.) (30-100° C.)

Glass transition point 240° C. (In the sample evaluation, those with thepoints of 160-300° C. were also used.)

Moisture absorption rate 0.91% 22° C., 60% RH)

Next, to explain the main processes of the manufacturing method for thepackage shown in FIG. 38, first, after the passivation film 13 isselectively etched to expose the bonding pads (FIG. 41), a noncuredthermoplastic polyimide resin 54A is painted on the entire face (FIG.42).

Next, an etching mask 20 of a photoresist is formed in the prescribedpattern by ultraviolet radiation and developing processes (FIG. 43).Using this mask 20, the polyimide resin 54A is wet etched and thebonding pads 1 are exposed (FIG. 44). After removal of the mask 20, thecuring is performed, producing the polyimide protective film 54.

The package that is manufactured in this manner has the superioradvantages, but it can be seen that there are still problems that mustbe alleviated. As for these problems, they are mainly generated in theetching process of the polyimide resin 54A shown in FIGS. 43 and 44,which are explained in detail in FIG. 44.

Namely, because the thermoplastic polyimide resin 54A is anon-photosensitive type (even though exposed, it is not madephotosensitive), it would be ideal for the etching to be done at thesame window size as mask 20 shown by the broken line in FIG. 45(A), butbecause it depends on wet etching, in actuality, overetching occurs asin FIG. 45(B). Due to this, there are instances wherein the polyimideresin 54 between adjacent bonding pads 1--1 is completely eliminated.

In the event that the thickness of the polyimide resin 54 is 20 μmbefore curing 10 μm thickness after curing) and the size of the bondingpad 1 is 100 μm×100 μm, the amount of overetching becomes as high as20-30 μm, the polyimide resin 54 between adjacent bonding pads 1--1 iseasily removed by the etching, and the passivation film 13 is exposed.

As a result, when sealing is done by means of molding resin 18 as shownin FIG. 38, this molding resin (for example, a multipurpose type ofepoxy resin) 18 comes in direct contact with the passivation film 13,but because the molding resin 18 has poor adhesion characteristics withthe Si₃ N₄ film 13A of the passivation film 13, fissures are generatedin the Si₃ N₄ film 13A by the stress due to heat, and become a cause ofpackage cracking. The problems due to the overetching in this manner arealso generated in the same manner even in the etching of thethermosetting polyimide resin 14A shown in FIGS. 32 and 33, and the sametypes of defects as the are created.

This invention should eliminate defects such as the, and its purpose isto offer a semiconductor device and its manufacturing method for apackage construction that can prevent chip cracking and wiring breakageafter the pressure-bonded mounting of the lead frame and during thethermal cycles, that controls the package cracking and package warpagein processes such as IR reflow and resin sealing, and that can be doneat a low cost.

SUMMARY OF THE INVENTION

The present inventors, when conducting various investigations in regardto the invention of the previous application, discovered the fact thatin the construction wherein the lead frame is directly pressure-bondingmounted on top of the polyimide resin layer used as the protective film,if a photosensitive thermosetting polyimide resin is used as the resinduring its patterning, there is no need to conduct wet etching using anetching mask like that mentioned above, and the patterning can be doneto the targeted configuration by means of only exposure and developingprocesses, thus they arrived at this invention.

In other words, this invention relates to a semiconductor device whereinthe lead frame is affixed to the semiconductor chip through the mediumof a photosensitive thermosetting resin layer such as a photosensitivethermosetting polyimide resin.

According to the semiconductor device of this invention, since aphotosensitive thermosetting resin layer, specifically a photosensitivethermosetting polyimide resin layer, is used in affixing the lead frameon top of the semiconductor chip at the time of forming the windows thatexpose the bonding pads by, for example, patterning this resin layer,the windows can be formed simply by exposing the photosensitivethermosetting resin layer to the targeted pattern, then developing it.

Therefore, since there is no generation of overetching like thatmentioned above, for example, the photosensitive thermosetting resinlayer on top of the passivation layer between adjacent bonding pointscan be removed, the adhesion of the molding resin can be excellentlymaintained, and package cracking can be prevented. As for thisphotosensitive thermosetting resin layer, due to the fact that the leadframe is bonded after the thermal curing via thermal pressure, theadhesion strength for the lead frame is generated, and the affixing ofthe lead frame can be excellently conducted.

In this case, if the surface roughness Ra of the photosensitivethermosetting polyimide resin layer is made greater than 3.0 nm, theadhesion for the lead frame increases. This type of surface roughnesscan be obtained by means of plasma etching the resin surface after thethermal curing.

Also, if the glass transition point of the photosensitive thermosettingpolyimide resin is made 245 to 350° C., since the adhesive function canbe maintained even during heating such as the IR reflow (at a reflowtemperature, for example, of 245° C.), package cracks can be positivelyprevented.

Also, in the semiconductor device of this invention, since the leadframe is adhered through the medium of a photosensitive thermosettingresin layer, the thickness of the adhesive layer required for mountingthe lead frame can be made smaller. Because of this, along with beingable to prevent the metal wiring breaks due to the thermal stressgenerated after the pressure-bonded mounting and during thermal cycles,the package cracks that have a tendency to be generated during IR reflowcan be reduced and a package balance is easily obtained (reduction ofpackage warpage), and cost reductions can be accomplished.

In the semiconductor device of this invention, specifically, aphotosensitive thermosetting resin layer is provided as a secondprotective film (in particular, a second protective film that alleviatesthe influence of α-rays due to the filler of the molding resin) on topof the protective film for the semiconductor chip, the lead frame isaffixed to the surface of this photosensitive thermosetting resin layer,and this lead frame is electrically connected to the circuits of thesemiconductor chip.

Also, the lead frame and the bonding pads for the semiconductor chipthat are present in a region wherein the photosensitive thermosettingresin layer has been selectively removed are wire bonded, and the entirebody is sealed with a molding resin.

The lead frame can be comprised of a lead frame section used for signallines and a lead frame section used for power-supply lines.

Also, the lead frame has an inner lead section, an outer lead section,and a support pin section. In the event that only this support pinsection is affixed to the photosensitive thermosetting resin layer,because the contact surface area of the lead frame in relation to thesemiconductor chip can be reduced by a wide margin, the stress that canbe generated on the semiconductor chip is greatly reduced and, forexample, the breakage of the metal wiring during the thermal cycles canbe prevented.

In this case, it is preferable that the inner lead section be separatedby being positioned at a spacing of 0.010-0.20 mm from the surface ofthe photosensitive thermosetting resin layer.

Also, the photosensitive thermosetting resin layer consists of apolyimide resin and the thickness is 20-40 μm. If it is greater than 30μm, the radiation α-rays from the filler of the molding resin issufficiently shielded, which is preferable for preventing soft errors.

This invention also offers a manufacturing method for a semiconductordevice consisting of a process that coats a photosensitive thermosettingresin layer on top of a semiconductor chip, a process that hardens thisphotosensitive thermosetting resin layer that has been coated in aprescribed pattern by light exposure, a process that removes thenonexposed sections of the photosensitive thermosetting resin layer, aprocess that thermally cures the photosensitive thermosetting resinlayer that remains on top of the semiconductor chip after this removalprocess, and a process that bonds via thermal pressure, a lead frame ontop of this thermally cured photosensitive thermosetting resin layer.

In this manufacturing method, it is preferable that after thethermosetting process the surface of the photosensitive thermosettingresin layer be processed by plasma etching, and that the lead frame bebonded via thermal pressure on the surface of the photosensitivethermosetting resin layer that has been processed by this plasmaetching.

Also, it is preferable that a photosensitive thermosetting resin layerbe coated on top of the protective film for the semiconductor chip, andthat this photosensitive thermosetting resin layer that has been coatedbe cured by ultraviolet rays to form a prescribed pattern.

Also, it is preferable for the lead frame and the bonding pads of thesemiconductor chip that are present in the region wherein thephotosensitive thermosetting resin layer has been selectively removed tobe wire bonded, and for the entire body to be sealed with a moldingresin.

DESCRIPTION OF EMBODIMENTS

Below, embodiments of this invention are explained.

FIGS. 1-24 show Embodiment 1, wherein this invention is applied, forexample, to a package for a DRAM. However, the components that areinvolved in the example shown in FIGS. 28-45 have the same keys, sotheir explanations are omitted [here].

First, an explanation will be given for the construction of a packagefor an LOC construction based on this embodiment with FIGS. 1-5(however, FIGS. 1-4 show the package and FIG. 5 shows the lead frame).As for the distinctive characteristics of the construction of thispackage, photosensitive-type of thermosetting polyimide resin layer 64is laminated on top of the passivation film 13 for the IC chip 10. Also,in the same manner as the previously mentioned polyimide protective film14, along with preventing soft errors due to α-rays from the filler ofthe sealing resin 18, the lead frame 11 having bus bars 42, 43, signallines 44, 45 (inner lead section), and support pin sections 60, 61, isbonded by thermal pressure (thermo-bonding mounted) on top of the resinlayer 64 only at the support pin sections 60, 61.

In other words, along with the photosensitive thermosetting polyimideresin layer 64 provided on top of the IC chip functioning as a secondprotective film in the same manner as the previously mentioned polyimideprotective film 14, the point should be noted that it functions as anadhesive for the lead frame 11 and that an insulating tape 15 like thatpreviously mentioned is not used.

Also, the lead frame 11, except for the support pin sections 60, 61, isin the condition of being separated by being placed a fixed spacing Cfrom the semiconductor chip 10, with only the support pin sections 60,61 that are folded to the semiconductor chip 10 side being affixed ontop of the semiconductor chip 10 by means of the resin layer 64. Also,the fact that the lead frame 11 is fastened by means of this should benoted. Here, the amount of folding of the support pin sections 60, 61 isequivalent to the spacing C, and can be 0.010 to 0.200 mm, for example,0.050 mm. The folding of the support pin sections in this way is called"downset" in the following description.

In FIG. 5, the lead frame 11 up to the position of the broken line 18 isresin-sealed along with the semiconductor chip; after the resin sealing,tie bar 70 is cut, then each lead section is separated.

Also, the photosensitive thermosetting polyimide resin layer 64 used asthe second protective film, as shown by the slanted lines in FIG. 3, isprovided across almost the entire region of the memory cell section ofthe IC. Also, in order to improve its adhesion, the surface of the resinlayer 64 is controlled to a surface roughness Ra of greater than 3.0 nmby plasma etching.

It is preferable that the thickness D of the polyimide resin layer 64 be20-40 μm, with above 30 μm being particularly preferable. Also, theglass transition point of the polyimide resin layer 64 can be above 245°C., specifically 245-350° C. The reasons for this are that, in the samemanner as mentioned above, the temperature during the thermal pressurebonding of the lead frame to the IC chip surface is less than 400° C.and the wire bonding temperature is 200° C.

Also, as for the size of each component, when looked at in regard to theentire package, specifically, these can be designed as shown in thefollowing Table III.

                  TABLE III                                                       ______________________________________                                        1 mm TSOP           2.7 mm SOJ                                                ______________________________________                                        A      0.195 mm (195 μm)                                                                           0.810 mm (810 μm)                                  B      0.125 mm (125 μm)                                                                           0.200 mm (200 μm)                                  C      0.050 mm (50 μm)                                                                            0.050 mm (50 μm)                                   D      0.020 mm (20 μm)                                                                            0.020 mm (20 μm)                                   E      0.260 mm (260 μm)                                                                           0.260 mm (260 μm)                                  F      0.350 mm (350 μm)                                                                           1.360 mm (1360 μm)                                 H      0.390 mm (390 μm)                                                                           1.080 mm (1080 μm)                                 I      0.350 mm (350 μm)                                                                           1.360 mm (1360 μm)                                 J      15.240 mm (15,240 μm)                                                                       15.240 mm (15,240 μm)                              ______________________________________                                    

As for the package based on this example, because it is a constructionwherein the lead frame 11 is directly pressure bonding mounted on top ofthe photosensitive thermosetting polyimide resin layer 64 used as theprotective film, in addition to the following effects (A) to (E), thefollowing superior affects (F) to (J) can also be obtained.

(A) The metal wire breakage generated after pressure-bonding mountingand during the thermal cycles can be prevented.

Because the insulating tape used in mounting until now was as thick as75 to 175 μm, the thermal stress was large, but because the thickness ofthe polyimide resin layer 64 is as small as 20-40 μm, the tensile stresscan be reduced by as much as 30% compared to the type used until now.

In particular, because the maximum stress concentrates in the chipsurface region directly beneath the corner section P of the bus barshown in FIG. 3 in the package inner sections, the tensile stress due tothis exerts a harmful influence on the device characteristics. When thetensile stress on top of the chip surface during a thermal cycle of150-65° C. was examined, in the construction of FIG. 3, a tensile stressof 2.90 kg/mm² was shown. It can be seen that this is also decreasedabout 30% compared to the tensile stress in the construction of FIG. 29based on the prior example, which is 4.20 kg/mm².

(B) The package cracks that have a tendency to be generated during theIR reflow can be prevented.

Along with being able to reduce the volume of the adhesive layer(polyimide resin layer), since the moisture content is reduced, thegeneration of package cracks during the IR reflow can be remarkablyreduced or prevented. In this case, there were no package cracks for asample of 120 units.

(C) Package warpage can be prevented.

In particular, in a 1-mm TSOP or the like, it becomes easy to obtain abalance of the resin thickness above and below the chip within thepackage due to the equilibrium between the thicknesses (H) and (I), thepackage warpage can be reduced to 20-40 μm or less, and can besufficiently prevented.

(D) Cost reductions can be realized.

Compared to the cost of the insulating tape (lead frame attachment) useduntil now, in the mounting construction based on this example, the perunit [cost] can be reduced to less than about 1/7 to 1/33.

(E) Soft errors can be effectively prevented.

Due to the fact that the thermosetting polyimide resin layer 64 isprovided at a thickness of above 20 μm across almost the entire regionof the cell section, the cell section is sufficiently shielded fromα-rays. Therefore, the α-rays radiated from the lead frame and thefiller (SiO₂ or the like) within the molding resin 18 are effectivelyblocked, and soft errors of the memory cell section can be prevented.

(F) The overetching of the polyimide resin layer can be reduced by awide margin.

Because the thermosetting polyimide resin layer 64 is a photosensitivetype, as is clear from the later presented manufacturing process, thewindows can be formed on top of the bonding pads simply by exposing thisphotosensitive thermosetting polyimide resin layer in the targetedpattern, then developing it.

Therefore, there is no generation of overetching like that shown in FIG.45(B). Also, since the amount of overetching during the patterning ordeveloping process and the like is an extremely small 2-5 μm, asufficient amount of photosensitive thermosetting polyimide resin layer64 can be left on top of the passivation film 13 between adjacentbonding pads 1--1, as shown in FIG. 45(A). Also, the adhesion for themolding resin can be excellently maintained and package cracks can beprevented.

(G) The breakage of the metal wiring can be prevented to a greaterextent.

The lead frame 11, having the inner lead sections 44, 45, outer leadsections 44a, 45a, and support pin sections 60, 61 is affixed to thephotosensitive thermosetting polyimide resin layer 64 only at thesupport pin sections 60, 61 downset, the contact surface area of thelead frame 11 with the semiconductor chip 10 is reduced by a widemargin, the stress that can be generated on the semiconductor chip 10 isgreatly reduced, and breakage of the metal wiring during the thermalcycles can be prevented to a greater extent. Since the lead frame 11 canbe sufficiently affixed by means of only affixing the support pinsections 60, 61, there is no necessity to affix the inner lead sectionto the semiconductor chip by an adhesive tape.

(H) Package cracking can be prevented to a greater extent.

Because the glass transition point of the photosensitive thermosettingpolyimide resin layer 64 is above 245° C., specifically 245 to 350° C.,and because the moisture content is less than 1.5%, the adhesivefunction can be maintained even during heating, such as during the IRreflow (at a reflow temperature for example, of 245° C.), and thepackage cracking can be positively prevented to a greater extent.

(I) The adhesion of the lead frame is improved.

As for the photosensitive thermosetting polyimide resin layer 64, anadhesive force is generated for the lead frame 11 due to the fact thatthe lead frame 11 is thermal-pressure bonded after the thermal curing,and the affixing of the lead frame can be excellently conducted. In thiscase, since the surface roughness (Ra) of the photosensitivethermosetting polyimide resin layer 64 is made greater than 3.0 nm, theadhesion for the lead frame 11 is improved. This type of surfaceroughness can be obtained by plasma etching the resin layer surfaceafter thermal curing.

(J) The resin sealing can be excellently conducted.

In the wire bonding of the lead frame 11, its inner lead sections 44, 45are bent and clamped to the semiconductor chip 10 side. However, afterthe wire bonding, they return to the original shape due to their elasticrecovery force and, as shown in FIG. 1, return to a position that isseparated by being placed at a spacing C in relation to thesemiconductor chip 10.

Because of this, during the later resin sealing, the peripheral sectionof the lead frame 11 is clamped by a metal mold. At the time ofinjecting the melted resin, even though the lead frame (specifically,the inner lead frame sections) is made to expand by the heat andpressure, because lead frame 11 is separated from the semiconductor chip10, there is no generation of stress between the semiconductor chip 10even by the expansion of the lead frame 11. As a result, there is nodestruction of the chip, warping of the package, or the like, and theresin sealing can be conducted with a good reliability. Also, theparasitic capacitance between the bit line of the chip 10 and the leadframe 11 is reduced, and is effective against soft error defects.

In contrast, in the event that the lead frame 11 is affixed to thesemiconductor chip 10 (refer to FIG. 29), there are instances ofdestruction of the semiconductor chip 10, warping of the package, andthe like by the stress due to the expansion of the lead frame. Also, anincrease in the parasitic capacitance and soft errors is easilygenerated.

The photosensitive thermoplastic polyimide resin 64 used in thisembodiment has the following physical values. It can comprise thestructural model shown in FIG. 6, which can be obtained by thepolyimidization of a precursor. This is an ester coupled type, but anion coupled type or the like can also be used.

Tensile strength 10 kg/mm² (room temperature)

Tensile modulus of elasticity 280 kg/mm² (room temperature)

Tensile coefficient of elongation 10% (room temperature)

Volume resistivity 6.3×10¹⁸ Ω-cm

Leakage current value 1.61×10⁻¹¹ (A) (room temperature) 1.07×10⁻¹¹ (A)(PCT after 500 h)

(The PCT (Pressure Cooker Test) test is one stress testing methodwherein the body to be tested is placed at a pressure of 1 atm and 121°C., and the changes in various characteristics before and afterwards areobserved.)

Pyrolysis temperature 520° C.

Thermal expansion coefficient 4.3×10⁻⁵ (1/°C.) (30-100° C.)

Glass transition point 245° C.

Moisture absorption rate 0.91% 22° C., 60% RH)

Next, to explain the main processes of the manufacturing method for thepackage shown in FIGS. 1-3, first, after selectively etching thepassivation film 13 (a laminated film of Si₃ N₄ film 13A and SiO₂ film13B) to expose the bonding pads 1, a noncured photosensitivethermosetting polyimide resin layer 64A) is coated on the entire surfaceto a dry thickness of 20 to 45 μm (FIG. 8).

Next, using exposure mask 70, the polyimide resin layer 64A isselectively exposed by means of ultraviolet rays 71 (FIG. 9) andnoncured section (the nonexposed section) is removed by a developingprocess (FIG. 10, leaving this section that has been hardened by theexposure.

In this manner, the bonding pads 1 are exposed, then the polyimideprotective film 64 is formed by a curing process by heating (FIG. 11).The processing conditions for this thermal curing can be 300-350° C.,for 2-4 h, and in air or in an N₂ gas flow. This polyimide protectivefilm 64 has a thickness of 20-40 μm and a glass transition point ofabove 245° C. (below 350° C.)

Next, the surface of the polyimide protective film 64 is bombarded byplasma 72 via CF₄ or a mixed gas of CHF₃ and CF₄. This is plasma etched,then the surface is suitably roughened so that the surface roughness Rabecomes greater than 3.0 nm.

Next, on top of the roughened surface of the polyimide protective film64, as shown in FIGS. 1-3, the support pin sections 60, 61 (downsetamount is 0.010-0.20 mm) of the lead frame 11 (made of 42 alloy) areaffixed on top of the semiconductor chip 10 by thermal-pressure bondingat 350° C.×4 kg.

Next, after the inner lead sections 44, 45 and bus bars 42, 43 of thelead frame 11 are wire bonded by wires (99.99% gold) to the bonding pads1, ejection molding is done with a thermosetting molding resin such as amultipurpose type of epoxy resin, then thermal hardening (curing) isexecuted at 175° C.×5 h.

The obtained package is an SOJ 34 pin type of 600 (width)×875(length)×106 (height) mil (see FIGS. 1-3).

On packages of the present application examples explained above, severalevaluations were conducted below.

IR Reflow Test

The results of IR reflow (max 245° C.) after being left at 85° C./85% RHfor 336 h are as follows. There were no problems of package cracking.This is because the glass transition point of the thermosettingpolyimide resin 64 was set high and the moisture content was set below1.0%.

This embodiment Prior example (FIG. 29)

Failure rate 0/120 16/120

Thermal Cycle Test (-65-150° C.)

The results of the thermal cycle test are as follows. There were noproblems of package cracking.

    ______________________________________                                                  This embodiment                                                                         Prior example (FIG. 29                                    ______________________________________                                        Failure rate                                                                              0/20        0/20                                                  for 2000 cycles                                                               ______________________________________                                    

Soft Error

Due to the fact that the thickness of the thermosetting polyimide resinlayer 64 is made 20-40 μm, as shown in FIG. 13, the soft errors due tothe α-rays, such as the ASER (Accelerated Soft Error Rate) of the 4 MDRAM, is remarkably reduced. In contrast, because the soft error becomeslarge with the film thickness of the same resin layer at less than 20μm, it is desirable that the film thickness be made greater than 20 μm.

In this case, as shown in FIG. 13, if the lead frame 11 isthermal-pressure bonded to the surface of the resin layer 64 on top ofthe IC chip surface, the lead frame 11 sinks into the resin layer 64only to the depth of about 10 μm. Because of this, in the event that thethickness of the thermosetting polyimide resin layer 64 is set to lessthan 30 μm, ASER problems are easily generated.

As was explained in the, in order to prevent ASER (Accelerated SoftError Rate) failures, a coating material of greater than 20 μm (beforemounting, greater than 30 μm) on top of the cell section of the IC chipis necessary.

In the prior construction (FIG. 29), since only a coating material(polyimide layer) 14 with a 10 μm thickness was coated on top of thecell section of the chip, as an ASER countermeasure, processing wasexecuted to suppress the amount of uranium and thorium to less than 1ppb of the silica contained in the mold sealing material.

With this as the cause, the price of the mold sealing material was twiceas high as normal. However, in this embodiment, because thethermosetting polyimide 64 is coated to a thickness of greater than 20μm on the cell section, preferably greater than 30 μm, there is no worrywith regard to ASER failures, and due to the fact that ordinary sealingmaterials (with amounts of uranium and thorium of 100 ppb) can be used,it has become possible to halve that cost.

Parasitic Capacitance

In the event of using the lead frame in the bit line of a DRAM, even inorder to suppress the problem of parasitic capacitance (bit-line to leadframe capacitance) to less than 1 pF, as shown in FIG. 14, it isnecessary for the thickness of the thermosetting polyimide resin layer64 to be greater than 30 μm. It can be seen that it is necessary for itto be greater than 20 μm after the lead-frame pressure bonding.

The curve shown in FIG. 14 was derived using the following equation.

    C=4πε.sub.0 ε/1n 4t2

with

t: polyimide thickness

ε: polyimide dielectric rate (3.3)

ε₀ : dielectric rate of vacuum

C: capacitance

Package Warpage

In the event the photosensitive type of processing polyimide resin 64 ontop of the passivation film is made at a thickness exceeding 40 μm afterthermal curing, because a warpage of 800 μm is generated in a 6-inwafer, it is necessary for the polyimide resin 64 to be made at lessthan 40 μm thick.

The increase in the warping of the wafer brings about an increase in itsinternal stress. The internal stress can be determined with thefollowing equation. In FIG. 15, the warped of the wafer is shown.

    δ(stress)=D.sup.2 E/6Rt(1-v)

with R(radius of curvature)=(a² +4X²)/8X

X: warpage of wafer

a: length of the arc of the warped wafer

D: wafer thickness (280 μm)

E: Si (wafer) modulus of elasticity (16200 kg/mm²)

t: polyimide resin film thickness

v: Poisson ratio (0.3)

The internal stress of the wafer changes as follows, depending on thethickness of the polyimide resin film. In order to make the internalstress of the wafer less than 2 kg/mm², it is necessary to make thepolyimide resin film thickness less than 40 μm (in the event theinternal stress of the wafer is made greater than 2 kg/mm², faults inthe Si crystals and the like are generated, bringing about harmfuleffects on the reliability).

    ______________________________________                                        Polyimide thickness (μm)                                                                    Wafer internal stress                                        ______________________________________                                        20               1.04 kg/mm.sup.2                                             30               1.73 kg/mm.sup.2                                             40               2.08 kg/mm.sup.2                                             50               2.29 kg/mm.sup.2                                             ______________________________________                                    

From the viewpoint of the ASER failures, parasitic capacitance, andwafer warpage, it is necessary and desirable for the film thickness ofthe polyimide resin film on top of the passivation film to be within20-40 μm.

In the TSOP package shown in FIG. 1, when the mold sealing resinthickness on the chip upper face is 0.390 mm, and the mold sealing resinthickness on the chip lower face is made 0.350 mm, because the values ofthe resin thickness above and below are close, the package warpagebecomes 20-40 μm.

Also, as can be understood from the package internal construction shownin FIGS. 1 and 2, it is preferable that the inner lead section of thelead frame 11, through which the current flows, be separated from thesurface of the polyimide resin layer film 64 by 0.010-0.20 mm. In otherwords, it is preferable for the support pin sections 60, 61 of the leadframe 11, through which the current does not flow, to be bent within arange of 0.10 to 0.20 mm (downset amount) and adhered to the surface ofthe polyimide resin film 64.

The reason for this is because, at the same time as more positivelymaintaining stability in regard to the parasitic capacitance between thebit line and lead frame, as well as the ASER failures, the stress of thechip surface is relieved.

Tensile Stress

In a 600×875×106 mil (width×length×height) package, in its internalsection, the maximum stress is concentrated in the chip surface regiondirectly below the corner sections (P) of the bus bar shown in FIG. 3,with the tensile stress due to this exerting a harmful influence on thedevice characteristics. When the maximum tensile stress on the chipsurface directly below the lead frame during a thermal cycle of 150° C.to -65° C. is found, in the construction of FIG. 3, a tensile strengthof 2.19 kg/mm² is shown. It can be seen that it is fairly reducedcompared to the construction of FIG. 29 based on the prior examplewherein the tensile stress is 4.20 kg/mm², and compared to theconstruction of FIG. 38 wherein the tensile stress is 3.31 kg/mm².

As for the photosensitive thermosetting polyimide resin, in a crack testunder thermal cycles (-65 to 180° C.), there were no cracks up to 3000thermal cycles, and a mechanical potential energy of 800 kg/mm² wasshown.

Here, the mechanical characteristics were found by the followingformulas (the sample was made 3 mm wide, 10 μm thick, and 50 mm long,and tension was applied at 40 mm/min and measured with a tension testingmachine Sub Pulser FB made by Shimadsu Seisakusho).

    ______________________________________                                        Destruction stress =                                                                       F (force applied to both ends of                                              the polyimide)/W · T                                                 W (width of test sample)                                                      T (thickness of test sample)                                     Elongation =                                                                            L2 (deformation at destruction point)/L × 100                           L (length of test sample)                                           Modulus of elasticity =                                                                     (L × S2/(W × T × L1)                                        S2 (destruction point stress)                                                 L1 (destruction point deformation)                              ______________________________________                                    

The surface area was found for the bottom section of the stress anddeformation curve derived by these means, which is called the mechanicalpotential energy of the polyimide, and was found by the formulaexpressed as: ##EQU2## Overetching

Because the photosensitive thermosetting polyimide resin is cured bybringing about a chemical reaction by photosensitive agents within thepolyimide resin layer with ultraviolet rays (UV), at the time ofpatterning, the resist mask used in the wet etching of anonphotosensitive type of polyimide resin becomes unnecessary. At thetime of the wet etching of a nonphotosensitive type of thermoplasticpolyimide resin, an alkaline etching liquid passed the boundary betweenthe resist and the polyimide layer, generating overetching, which becamea problem. However, because there is no wet etching with thephotosensitive thermosetting polyimide resin, and because the patterningis done by developing after exposure, overetching is almost not seen.For example, in the etching of a polyimide film of 10 μm thickness aftercuring on top of a 100 μm×100 μm bonding pad, the window becomes onlyabout 2 to 5 μm larger.

Adhesive Strength

The following tests were conducted in regard to the adhesion between apolyimide resin surface and alloy 43 (lead frame material). The sampleof the polyimide resin was made in the following manner. Following theprocess flow shown in FIGS. 7-12, the execution of the coating, UVexposure, and developing, the curing conditions for the polyimide resin,and the plasma etching conditions (gas used for etching) were set asfollows.

Curing conditions: temperature 350° C. (2 h), 390° C. (1 h)

Atmosphere: N₂ gas, air flow

Plasma etching conditions: CHF₃ /CF₄, CF₄, none

The following seven types of samples were then made. In all of these,the thickness after curing was set to 10 μm.

    ______________________________________                                               Curing conditions                                                      Sample No.                                                                             Temperature                                                                              Atmosphere Plasma conditions                              ______________________________________                                        1        350° C.                                                                           N.sub.2    None                                           2        350° C.                                                                           N.sub.2    CF.sub.4                                       3        390° C.                                                                           N.sub.2    None                                           4        390° C.                                                                           N.sub.2    CF.sub.4                                       5        390° C.                                                                           Air        None                                           6        390° C.                                                                           Air        CF.sub.4                                       7        390° C.                                                                           N.sub.2    CHF.sub.3 /CF.sub.4                            ______________________________________                                    

After dicing and cutting off the respective samples to a width of2.5±0.05 cm, the cutoff sections were bonded in a 23% HF solution, thenthe polyimide resin film was pulled from the wafer. The respectivepolyimide resin films, after washing with pure water, were dried for 1 hat 55° C.

Each of these polyimide resin films, as shown in FIG. 16, were thenplaced between a pair of heaters and thermal-pressure bonded with analloy 42 flat surface plate of 200 μm thickness. These thermal-pressurebonding conditions were as follows.

Thermal-pressure bonding temperatures: 280, 310, 330, 370, 400° C.

Thermal-pressure bonding pressures: 3.0 kg/cm², 6.0 kg/cm²

Thermal-pressure bonding times: 3 sec, 6 sec

As shown in FIG. 17, each of the following measurements were done inregard to the adhesive strength, based on the 90° peeling test method ofISO Regulations 4578-1979, then the adhesive strength at the polyimideresin/alloy 42 boundary was found. The results are shown in thefollowing Tables IV-IX.

                  TABLE IV                                                        ______________________________________                                                Pressure   Pressure  Pressure                                                 bonding    bonding   bonding                                                                              Adhesive                                  Sample No.                                                                            temperature                                                                              pressure  times  strength                                  ______________________________________                                        1       280° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec   0 g/cm                                                                6 sec   0 g/cm                                                      6.0 Kg/cm.sup.2                                                                         3 sec   0 g/cm                                                                6 sec   0 g/cm                                           310° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec  130 g/cm                                                               6 sec  204 g/cm                                                     6.0 Kg/cm.sup.2                                                                         3 sec  148 g/cm                                                               6 sec  130 g/cm                                          330° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec  371 g/cm                                                               6 sec  390 g/cm                                                     6.0 Kg/cm.sup.2                                                                         3 sec  501 g/cm                                                               6 sec  501 g/cm                                          370° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec  >1200 g/cm                                                             6 sec  >1200 g/cm                                                   6.0 Kg/cm.sup.2                                                                         3 sec  >1200 g/cm                                                             6 sec  >1200 g/cm                                        400° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec  >1200 g/cm                                                             6 sec  >1200 g/cm                                                   6.0 Kg/cm.sup.2                                                                         3 sec  >1200 g/cm                                                             6 sec  >1200 g/cm                                ______________________________________                                    

                  TABLE V                                                         ______________________________________                                              Pressure  Pressure                                                      Sample                                                                               bonding  bonding    Pressure Adhesive                                  No.   temperature                                                                             pressure   bonding times                                                                          strength                                  ______________________________________                                        2     280° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    167   g/cm                                                           6 sec    130   g/cm                                                6.0 Kg/cm.sup.2                                                                          3 sec    130   g/cm                                                           6 sec    204   g/cm                                      310° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    >1200 g/cm                                                           6 sec    >1200 g/m                                                 6.0 Kg/cm.sup.2                                                                           3 sec   >1200 g/cm                                                           6 sec    >1200 g/cm                                      330° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    >1200 g/cm                                                           6 sec    >1200 g/cm                                                6.0 Kg/cm.sup.2                                                                          3 sec    >1200 g/cm                                                           6 sec    >1200 g/cm                                      370° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    >1200 g/cm                                                           6 sec    >1200 g/cm                                                6.0 Kg/cm.sup.2                                                                          3 sec    >1200 g/cm                                                           6 sec    >1200 g/cm                                      400° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    >1200 g/cm                                                           6 sec    >1200 g/cm                                                6.0 Kg/cm.sup.2                                                                          3 sec    >1200 g/cm                                                           6 sec    >1200 g/cm                                ______________________________________                                    

                  TABLE VI                                                        ______________________________________                                                Pressure   Pressure  Pressure                                                 bonding    bonding   bonding                                                                              Adhesive                                  Sample No.                                                                            temperature                                                                              pressure  times  strength                                  ______________________________________                                        3       280° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec   0 g/cm                                                                6 sec   0 g/cm                                                      6.0 Kg/cm.sup.2                                                                         3 sec   0 g/cm                                                                6 sec   0 g/cm                                           310° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec  140 g/cm                                                               6 sec  167 g/cm                                                     6.0 Kg/cm.sup.2                                                                         3 sec  111 g/cm                                                               6 sec  149 g/cm                                          330° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec  278 g/cm                                                               6 sec  297 g/cm                                                     6.0 Kg/cm.sup.2                                                                         3 sec  297 g/cm                                                               6 sec  538 g/cm                                          370° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec  374 g/cm                                                               6 sec  409 g/cm                                                     6.0 Kg/cm.sup.2                                                                         3 sec  520 g/cm                                                               6 sec  483 g/cm                                          400° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec  >1200 g/cm                                                             6 sec  >1200 g/cm                                                   6.0 Kg/cm.sup.2                                                                         3 sec  >1200 g/cm                                                             6 sec  >1200 g/cm                                ______________________________________                                    

                  TABLE VII                                                       ______________________________________                                                Pressure   Pressure  Pressure                                                 bonding    bonding   bonding                                                                              Adhesive                                  Sample No.                                                                            temperature                                                                              pressure  times  strength                                  ______________________________________                                        4       280° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec   0 g/cm                                                                6 sec   0 g/cm                                                      6.0 Kg/cm.sup.2                                                                         3 sec   0 g/cm                                                                6 sec   0 g/cm                                           310° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec  167 g/cm                                                               6 sec  260 g/cm                                                     6.0 Kg/cm.sup.2                                                                         3 sec  278 g/cm                                                               6 sec  297 g/cm                                          330° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec  427 g/cm                                                               6 sec  445 g/cm                                                     6.0 Kg/cm.sup.2                                                                         3 sec  650 g/cm                                                               6 sec  575 g/cm                                          370° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec  >1200 g/cm                                                             6 sec  >1200 g/cm                                                   6.0 Kg/cm.sup.2                                                                         3 sec  >1200 g/cm                                                             6 sec  >1200 g/cm                                        400° C.                                                                           3.0 Kg/cm.sup.2                                                                         3 sec  >1200 g/cm                                                             6 sec  >1200 g/cm                                                   6.0 Kg/cm.sup.2                                                                         3 sec  >1200 g/cm                                                             6 sec  >1200 g/cm                                ______________________________________                                    

                  TABLE VIII                                                      ______________________________________                                              Pressure  Pressure                                                      Sample                                                                               bonding  bonding    Pressure Adhesive                                  No.   temperature                                                                             pressure   bonding times                                                                          strength                                  ______________________________________                                        5     280° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    0     g/cm                                                           6 sec    0     g/cm                                                6.0 Kg/cm.sup.2                                                                          3 sec    0     g/cm                                                           6 sec    0     g/cm                                      310° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    0     g/cm                                                           6 sec    0     g/m                                                 6.0 Kg/cm.sup.2                                                                           3 sec   121   g/cm                                                           6 sec    170   g/cm                                      330° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec     156  g/cm                                                           6 sec    150   g/cm                                                6.0 Kg/cm.sup.2                                                                          3 sec    262   g/cm                                                           6 sec    280   g/cm                                      370° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    440   g/cm                                                           6 sec    421   g/cm                                                6.0 Kg/cm.sup.2                                                                          3 sec    550   g/cm                                                           6 sec    573   g/cm                                      400° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    660   g/cm                                                           6 sec    620   g/cm                                                6.0 Kg/cm.sup.2                                                                          3 sec    >1200 g/cm                                                           6 sec    >1200 g/cm                                ______________________________________                                    

                  TABLE IX                                                        ______________________________________                                              Pressure  Pressure                                                      Sample                                                                               bonding  bonding    Pressure Adhesive                                  No.   temperature                                                                             pressure   bonding times                                                                          strength                                  ______________________________________                                        6     280° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    0     g/cm                                                           6 sec    0     g/cm                                                6.0 Kg/cm.sup.2                                                                          3 sec    0     g/cm                                                           6 sec    0     g/cm                                      310° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    204   g/cm                                                           6 sec    220   g/m                                                 6.0 Kg/cm.sup.2                                                                           3 sec   167   g/cm                                                           6 sec    242   g/cm                                      330° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec     260  g/cm                                                           6 sec    272   g/cm                                                6.0 Kg/cm.sup.2                                                                          3 sec    402   g/cm                                                           6 sec    417   g/cm                                      370° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    612   g/cm                                                           6 sec    600   g/cm                                                6.0 Kg/cm.sup.2                                                                          3 sec    720   g/cm                                                           6 sec    760   g/cm                                      400° C.                                                                          3.0 Kg/cm.sup.2                                                                          3 sec    >1200 g/cm                                                           6 sec    >1200 g/cm                                                6.0 Kg/cm.sup.2                                                                          3 sec    >1200 g/cm                                                           6 sec    >1200 g/cm                                ______________________________________                                    

A presentation is made later in regard to an evaluation of the resultsof the Tables IV-IX.

Glass Transition Point, Surface Roughness, & Surface ChemicalComposition of Photosensitive Thermosetting Polyimide Resin

The glass transition point was checked using a TMA measuring machinemade by the Shimadzu Seisakusho. The glass transition point is calledthe temperature at which the polyimide is transformed from the glasscondition to the gum condition.

The surface roughness was checked using a Nano Scope II Atomic ForceMicroscope (AFM) made by the Digital Instruments Co. In this case, theprobe tip angle was 20°, its length was 10 μm, and its material wasmonocrystalline silicon. Ra and RMax were found according to thedefinition of JIS B0601.

The surface chemical composition was checked using an ESCA-300 made by,the Seiko Denshi Co. The composition ratio was found for the CO--(carbonyl group) and the COO-- (carboxyl group) of the polyimidesurface. Beginning with the total ratio of the carbonyl group and thecarboxyl group of a polyimide surface of 2×2 mm², the physical propertyvalues of the polyimide are shown in the following Table X.

                  TABLE X                                                         ______________________________________                                        Physical property values of the polyimide                                                                 Surface Chemical                                  Glass                       Composition                                       Transition     Surface Roughness                                                                          Total CO and COO                                  Sample No.                                                                            Point (° C.)                                                                      R.sub.a (nm)                                                                          R.sub.max (nm)                                                                       (contents wt %)                             ______________________________________                                        1       260        2.52    33.06  08%                                         2       260        3.86    44.62  23%                                         3       330        2.48    30.52  08%                                         4       330        3.70    41.44  22%                                         5       350        1.90    24.27  06%                                         6       350        3.40    40.38  21%                                         7       330        3.11    39.04  19%                                         ______________________________________                                    

From the results of the above Tables IV-X, [it can be seen that] inorder to prevent the oxidation of a lead frame of alloy 42, it ispreferable that the temperature at which the lead frame is glued to thesurface of the chip (thermosetting polyimide resin) be less than 400° C.It is also preferable that the glass transition point Tg of thethermosetting polyimide resin be more than 50-100° C. lower than thetemperature at which the lead frame is glued (in other words, less than300-350° C.).

In other words, in improving the adhesive force, as for the temperatureat which the lead frame is glued (pressure bonding temperature), it canbe seen that in Table IV it can be above Tg (260° C.)+110° C., in TableV above Tg (260° C.)+50° C., in Table VI above Tg (330° C.)+70° C., inTable VII above Tg (330° C.)+40° C., and in Table VIII above Tg (350°C.)+50° C. These facts show that it is preferable for the glasstransition point (Tg) of the thermosetting polyimide resin to be morethan 50-100° C. lower than the temperature at which the lead frame isglued.

Also, it is better if the glass transition point of the thermosettingpolyimide resin is above the IR reflow temperature (245° C.). This isbecause in the event the glass transition point is below 245° C., thepolyimide resin shifts to the gum condition, and the adhesive force withthe mold sealing resin becomes poor.

From the above facts, [it can be seen that] it is preferable for theglass transition point of the photosensitive thermosetting polyimideresin to be 350-245° C.

Also, the fact that the surface roughness of the thermosetting polyimideresin affects the adhesive strength between a lead frame of alloy 42 andthe polyimide resin has been made clear from the experimental results.

In other words, the adhesive force is increased by making the surfaceroughness Ra of the polyimide resin above 3.00 nm by plasma processing.

An AFM photo is shown in FIG. 18 for a polyimide resin without plasmaprocessing (the Sample No. 3), and in FIG. 19 for a polyimide resinwherein the surface has been roughened by plasma processing (the SampleNo. 4).

The roughening of the surface results in a chemical coupling of thepolyimide resin being interrupted. Because the coupling force of theC--N, C--C, and C--O of the polyimide resin (Refer to FIG. 6 is weak,these are interrupted due to the plasma etching process as shown by (A),(B), and (C) in FIG. 20.

As a result, the data of the XPS (X-ray photoemission spectroscopy)shown in FIG. 22, compared to that of FIG. 21, show that the peaks of P1(C--C coupling) and P2 (C--O or C--N coupling) are reduced, and that thepeaks of P3 (C═O: carbonyl group and P4 (COO--: carboxyl group: this isthe interrupted portion at position (A) of FIG. 20 at which oxidation isgenerated) are increased. The assignment of the chemical coupling andthe coupling energy of the polyimide resin is shown in FIG. 23.

The wettability of the carbonyl group and carboxyl group with alloy 42is good, and hydrogen coupling is promoted. Because of this, the closeadhesion force is increased.

Electrical Characteristics

A 34 pin SOJ package was constructed having the internal constructionshown in FIGS. 1 and 2. In other words, a test chip having silicon, ametal, a passivation film (Si₃ N₄, SiO₂, and a thermosetting polyimideresin (with a 350° C. curing temperature, N₂ gas, CF₄ plasmaprocessing), respectively, was constructed like that of FIG. 24.

The physical properties of the thermosetting epoxy resin (used forsealing) and the photosensitive thermosetting polyimide resin used hereare shown below.

Thermosetting epoxy resin

Multipurpose type of epoxy resin

Bending strength 14.2 kg/mm² (room temperature)

Bending modulus of elasticity 1580 kg/mm² (room temperature)

Glass transition point 157° C.

Thermal expansion coefficient 10 ppm (1/°C.)

Photosensitive thermosetting polyimide resin

Tensile strength 15.6 kg/mm² (room temperature)

Tensile modulus of elasticity 300 Kg/mm² (room temperature)

Tensile modulus of elongation 48% (room temperature)

Percentage of water absorption 1.4% (22° C., 60% RH)

Permittivity 3.3

Glass transition point 260° C.

The test chip 80 of FIG. 24 was divided into a large number of blocks,both ends of the wiring 81 of a zigzag shape were connected to thebonding pads 82 within region A of each block, and a lead frame, omittedfrom the illustration, was affixed to the polyimide resin on top of thechip in an LOC construction. The continuity (measurement for whether thecircuit is open or shorted) and leakage (leakage current) were thenchecked by measuring the current value between the outer lead sections.As for the region B, wiring was installed for the chip corner sections,and as for region C, wiring used for connecting between the blocks wasinstalled, then measurements were conducted in the same manner as in theabove.

Specifically, an IR reflow test of 85/85 336 h [85° C./85% RH for 336h], thermal cycles (-65 to 150° C.), PCT (pressure cooker test) (2 atm,121° C.), and a test involving leaving it at a high temperature (175°C.) were done. The results are shown below.

    ______________________________________                                                Continuity/Leak electrical                                                    characteristics check                                                         (failure rate)                                                        ______________________________________                                                85/85 336 h IR reflow                                                         (MAX 245° C.) 0/30                                                     Temperature cycles                                                            (-65 to 150° C.) 1000 cycles 0/30                                      Left at high temperature                                                      (175° C.) 1000 h 0/30                                                  PCT (2 atm, 121° C.) 500 h 0/30                                ______________________________________                                    

From these results, the fact was made clear that there were no problemsin the continuity and leak checks.

FIG. 25 shows another embodiment wherein this invention was applied toan LOC construction.

In this embodiment, compared to the construction of FIG. 1, the factthat the lead frame 11, including the inner lead sections 44, 45, areaffixed by contacting the photosensitive thermosetting polyimide resinlayer 64, and the fact that the support pin [sections] 60, 61 are notdownset, are points of difference. The other factors are the same.

Therefore, in this embodiment the effects due to the usage of thepolyimide resin layer 64 can be obtained in the same manner as presentedin the embodiments. Also, as for the lead frame 11 itself, it becomespossible to use the same device as in products used until now, and thereis no need to use a process for the downset.

FIG. 26 shows another embodiment wherein this invention was applied toanother type of construction.

In other words, according to this embodiment, in a multipin QFP (QuadFlat Package), the IC chip mounting section 152 of a lead frame used asan LOC construction is thermal-pressure bonded on top of the IC chip 10with the photosensitive thermosetting polyimide resin layer 64interposed, the bonding pads on the periphery of the IC chip 10 are wirebonded to the inner lead sections 153, 154 by means of wires 150, 151,and the entire body is sealed with molding resin 158. Besides that, thefilm construction and the like beneath the resin layer 64 can be thesame as that presented in the embodiments.

Since the package according to this embodiment also does not use aninsulating tape with an adhesive on both sides, and-the lead frame ispressure mounted on top of the IC chip by means of the thermosettingpolyimide resin layer 64, the same types of effects as presented in theembodiments can be obtained.

In addition, since the wire bonding is conducted between the peripheryof the IC chip and the inner lead sections, as shown in FIG. 26, thewire contacts (shorts) to the chip, which have a tendency to begenerated in the event the inner lead section and the IC chip 10 affixedon top of the mounting section 152 of the lead frame are wire bonded,can be prevented.

FIG. 27 shows an embodiment wherein this invention is applied to a COL(Chip On Lead) construction.

According to this embodiment, the IC chip 10 is mounted on top of theinner lead sections 44, 45 of the lead frame 11 by means of thephotosensitive thermosetting polyimide resin layer 64, and is connectedbetween the chip 10 and lead frame 11 by the wire bonding from the chipupper section.

In this type of COL construction, package cracks and the like during IRreflow can be reduced by the usage of the resin layer 64. This isbecause the molding resin 18 has an excellent adhesive force with thepolyimide resin 64.

This invention was exemplified above, but as for the embodiments,further modifications are possible based on the technical concepts ofthis invention.

For example, the photosensitive thermosetting polyimide resin that wasused in the embodiments is not limited to those of the construction; itsconstruction components, physical characteristics, and the like can bevariously modified. Also, the usage of resins other than the polyimidetype is possible as long as they have equivalent physicalcharacteristics.

Also, as for the region that forms this resin layer, besides providingit almost entirely on top of the chip, it can also be provided locallyin the required locations. For example, it can be provided only on thesupport pin sections, but in this case it is necessary that the regionsother than that be covered with another second protective film.

This invention can be applied to other devices such as the TSOP type orSOJ type as a package. Furthermore, this invention can be applied notonly to a DRAM (16 megabyte, 64 megabyte, and the like), but also toother various devices.

This invention, as was presented above, uses a photosensitive type ofthermoplastic resin layer in affixing the lead frame on top of thesemiconductor chip, specifically a photosensitive thermosettingpolyimide resin layer. At the time of forming windows that expose thebonding pads, for example, by patterning this resin layer, it becomespossible to form the windows simply by exposing and developing thephotosensitive thermosetting resin layer in the targeted pattern.

Therefore, because the overetching like that mentioned above is notgenerated, for example, the photosensitive thermosetting resin layer canremain on top of the passivation film between adjacent bonding pads, theclose adhesion with the molding resin can be excellently maintained, andpackage cracks can be prevented. As for this photosensitivethermosetting resin layer, by means of thermal-pressure bonding the leadframe after thermal curing, an adhesive force for the lead frame isgenerated and the affixing of the lead frame can be excellentlyaccomplished.

Lastly, in the semiconductor device of this invention, since the leadframe is affixed with the photosensitive thermosetting resin layerinterposed, the thickness of the adhesive necessary in mounting the leadframe can be reduced. Due to this, along with being able to preventmetal wiring breaks due to the thermal stress generated after thepressure-bonding mounting and during the thermal cycles, the packagecracks that have a tendency to be generated during IR reflow arereduced, a package balance is easily achieved (reduction of packagewarpage), and a cost reduction can be accomplished.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view (of FIG. 4 through line I--I) of an ICpackage of a LOC construction based on an embodiment of this invention.

FIG. 2 is a cross-sectional view of this same package (of FIG. 4 throughline II--II).

FIG. 3 is an enlarged perspective view of the main components of thissame package.

FIG. 4 is a perspective view of the main components of this samepackage.

FIG. 5 is a plane view of the lead frame of this same package.

FIG. 6 is a drawing showing a construction formula of a photosensitivethermosetting polyimide resin.

FIG. 7 is a cross-sectional view showing one process of themanufacturing method for this same package.

FIG. 8 is a cross-sectional view showing another process of themanufacturing method for this same package.

FIG. 9 is a cross-sectional view showing another process of themanufacturing method for this same package.

FIG. 10 is a cross-sectional view showing another process of themanufacturing method for this same package.

FIG. 11 is a cross-sectional view showing another process of themanufacturing method for this same package.

FIG. 12 is a cross-sectional view showing yet another process of themanufacturing method for this same package.

FIG. 13 is a graph showing the soft error (failure rate) due to α-raysand an enlarged cross-sectional view of the package main components.

FIG. 14 is a graph showing the changes in the parasitic capacitance.

FIG. 15 is an abbreviated view for the purpose of explaining the waferwarpage.

FIG. 16 is a cross-sectional view of the process that bonds, by thermalpressure, the polyimide resin layer and the lead frame material.

FIG. 17 is a cross-sectional view of a sample for the purpose ofexplaining the conditions for the peel test.

FIG. 18 is a sketch of an AFM image of the polyimide resin (withoutplasma processing).

FIG. 19 is a sketch of an AFM image of the polyimide resin (with plasmaprocessing).

FIG. 20 is a drawing for the purpose of explaining the interruption ofthe chemical coupling of the polyimide resin.

FIG. 21 is a spectral analysis graph based on an XPS of the polyimideresin (without plasma processing).

FIG. 22 is a spectral analysis graph based on an XPS of the polyimideresin (with plasma processing).

FIG. 23 is an explanatory drawing showing the assignment in this sameXPS.

FIG. 24 is an abbreviated enlarged plane view of each section ofabbreviated plane views of the test chips.

FIG. 25 is a cross-sectional view of an IC package of an LOCconstruction based on another embodiment of this invention.

FIG. 26 is a cross-sectional view of an IC package based on anotherembodiment of this invention.

FIG. 27 is a cross-sectional view of an IC package of a COL constructionbased on yet another embodiment of this invention.

FIG. 28 is a perspective view of the main components of a package for anLOC construction used until now.

FIG. 29 is a cross-sectional view (of FIG. 28 through lines XXIX--XXIX)of this same package.

FIG. 30 is a cross-sectional view showing a process of the manufacturingmethod for this same package.

FIG. 31 is a cross-sectional view showing another process of themanufacturing method for this same package.

FIG. 32 is a cross-sectional view showing another process of themanufacturing method for this same package.

FIG. 33 is a cross-sectional view showing yet another process of themanufacturing method for this same package.

FIG. 34 is an enlarged cross-sectional view (of FIG. 28 through linesXXXIV--XXXIV) of the main components of this same package.

FIG. 35 is a graph showing the viscosity characteristics of thethermoplastic adhesive used in this same package.

FIG. 36 is an enlarged cross-sectional view of the main componentsduring the IR reflow tests for this same package.

FIG. 37 is an abbreviated lateral view showing the warpage condition ofthis same package.

FIG. 38 is a cross-sectional view of an IC package of an LOCconstruction based on an embodiment of the invention of the previousapplication.

FIG. 39 is an enlarged perspective view of the main components of thissame package.

FIG. 40 is a drawing showing the construction formula for thethermoplastic polyimide resin used in this same package.

FIG. 41 is a cross-sectional view showing a process of the manufacturingmethod for this same package.

FIG. 42 is a cross-sectional view showing another process of themanufacturing method for this same package.

FIG. 43 is a cross-sectional view showing another process of themanufacturing method for this same package.

FIG. 44 is a cross-sectional view showing yet another process of themanufacturing method for this same package.

FIG. 45 is an enlarged cross-sectional view of a bonding pad section ofthis same package.

In the figures, 1 is a bonding pad, 6, 7, 8, 9 wires, 10 an IC chip, 11a lead frame, 12 a silicon substrate, 13 a passivation film, 14 athermosetting polyimide resin layer, 15 an insulating tape, 16 aninsulating substrate, 15, 17 adhesives, 18 molding resin, 20 aphotoresist etching mask, 42, 43 bus bars, 44, 45 signal lines, 54 athermoplastic polyimide resin layer, 6 a photosensitive thermosettingpolyimide resin layer, 70 an exposure mask, 71 ultraviolet rays, and 72is a plasma.

I claim:
 1. A semiconductor device comprising:a semiconductor chiphaving electrical circuits; a tapeless mounting for a lead framecomprising: a photosensitive insulating thermosetting resin layeraffixed to the semiconductor chip and patterned to expose bond pad areason the chip; and a lead frame affixed to the semiconductor chip by thephotosensitive thermosetting, resin layer.
 2. A semiconductor devicecomprising:a semiconductor chip having electrical circuits: a tapelessmounting for a lead frame comprising: a photosensitive thermosettingresin layer affixed to the semiconductor chip: and a lead frame affixedto the semiconductor chip by the photosensitive thermosetting resinlayer, wherein the lead frame comprises an inner lead section, an outerlead section, and a support pin section, with only the support pinsection affixed to the photosensitive thermosetting resin layer.
 3. Thedevice of claim 2 further comprising:a protective film on thesemiconductor chip, on which the photosensitive thermosetting resinlayer is disposed.
 4. The device of claim 2 wherein the inner leadsection is separated by placing it at a spacing of about 0.010 to 0.20mm from the surface of the photosensitive thermosetting resin layer. 5.The device of claim 2 wherein the photosensitive thermosetting resinlayer comprises a polyimide resin 20 to 40 μm thick.
 6. The device ofclaim 5 wherein the glass transition point of the photosensitivethermosetting polyimide resin layer is 245-350° C.
 7. The device ofclaim 5 wherein the surface roughness (Ra) of the photosensitivethermosetting polyimide resin layer is less than 3.0 nm.
 8. The deviceof claim 2 wherein the semiconductor chip has bonding pads coupled tothe electrical circuit, and the lead frame and the bonding pads are wirebonded in a region wherein the photosensitive thermosetting resin layerhas been selectively removed and the semiconductor chip's entire body issealed with a molding resin.
 9. The device of claim 2 wherein the leadframe comprises a first lead frame section used for signal lines and asecond lead frame section used for power supply lines.
 10. Asemiconductor device comprising:a semiconductor chip having electricalcircuits; a tapeless mounting for a lead frame comprising: aphotosensitive thermosetting resin layer affixed to the semiconductorchip; and a lead frame affixed to the semiconductor chip by thephotosensitive thermosetting polyimide resin layer 20 to 40 μm thick,and having a glass transition point of 245-350° C.